A trio of new studies published in JAMA Internal Medicine on Tuesday examining the efficacy of an arthritis drug against Covid-19 showed inconsistent results.
Tocilizumab has been used by doctors since the start of the pandemic with the hope of tamping down an abnormal immune response known as a "cytokine storm" that causes severe organ damage in some hospitalized Covid-19 patients.
Unlike steroids, which suppress the immune system more broadly, tocilizumab blocks a particular signaling protein from triggering inflammation.
Of the three new studies, the largest was led by the Harvard-affiliated Brigham and Women's Hospital in the United States on more than 4,000 critically ill Covid-19 patients.
The risk of death at 30 days was 28 and 38 percent among tocilizumab-treated and non-tocilizumab-treated patients, respectively.
But the American study was "observational," meaning it didn't compare the drug, which was administered intravenously, with a standard treatment.
There were also key differences in the patient demographics among those who received tocilizumab - which the authors tried to control for using statistical methods - but the risk of confounding factors remains.
The two other studies, carried out in France and Italy, were randomized controlled trials, considered the gold standard for clinical research, in which patients are allocated a treatment by chance.
The Italian trial looked at around 120 patients and didn't find any difference in outcomes between those on tocilizumab.
The French trial looked at about 130 patients who weren't critically ill. The risk of death or progression to ventilators decreased in those on the drug by two weeks, but after 28 days mortality outcomes were similar.
Writing in a related editorial, Doctor Jonathan Parr, an infectious disease specialist at University of North Carolina at Chapel Hill said: "Newly released randomised trials suggest a potential role for tocilizumab in COVID-19 but do not show clear evidence of efficacy.
"I plan to wait out the torrent of positive observational studies and reconsider tocilizumab's use in Covid-19 if, and only if, more compelling data from randomized trials emerges."
The US National Institutes of Health currently does not recommend tocilizumab for use against Covid-19 outside of clinical trials, and Tuesday's results will unlikely change that.
Tocilizumab belongs to a class of drug called "monoclonal antibodies" which have received significant attention after US President Donald Trump received a dose of the lab-made molecules for his Covid-19.
However unlike the experimental drug devised by Regeneron which Trump received, tocilizumab is an already licensed drug for immune conditions.
Regeneron's treatment, and a similar therapy developed by Eli Lilly, target a surface protein of the coronavirus to stop it from invading human cells.
Tocilizumab instead blocks a receptor of Interleukin (IL)-6, a protein called a "cytokine" that signals the body to mount an inflammatory response against pathogens. – ETX Studio, October 21, 2020
